Phenolic compounds from vacuum pyrolysis of wood wastes

Pyrolytic Behavior of Major Biomass Components in Waste Biomass

The pyrolytic behavior of several biomass components including cellulose, hemicellulose, lignin, and tannin, from two sources of waste biomass (i.e., pine bark and pine residues) were examined. Compared to the two aromatic-based components in the biomass, carbohydrates produced much less char but more gas. Surprisingly, tannin produced a significant amount of water-soluble products; further analysis indicated that tannin could produce a large amount of catechols. The first reported NMR chemical shift databases for tannin and hemicellulose pyrolysis oils were created to facilitate the HSQC analysis. Various C⁻H functional groups (>30 different C⁻H bonds) in the pyrolysis oils could be analyzed by employing HSQC-NMR. The results indicated that most of the aromatic C⁻H and aliphatic C⁻H bonds in the pyrolysis oils produced from pine bark and pine residues resulted from the lignin and tannin components. A preliminary study for a quantitative application of HSQC-NMR on the characterization of pyrolysis oil was also done in this study. Nevertheless, the concepts established in this work open up new methods to fully characterize the whole portion of pyrolysis oils produced from various biomass components, which can provide valuable information on the thermochemical mechanisms.

In situ upgrading of whole biomass to biofuel precursors with low average molecular weight and acidity by the use of zeolite mixture

By using a designed mixture of zeolites (Y and mordenite), the upgraded pyrolysis oil exhibited the advantages caused from both zeolites, which represents a biofuel precursor has a very low molecular weight (70–170 g mol⁻¹) and a low acidity.

In situ NMR characterization of pyrolysis oil during accelerated aging

COMING OF AGE: A method for investigating the accelerated aging of biomass pyrolysis oils is reported. The in situ NMR investigation, done by using quantitative ¹H, ¹³C NMR and heteronuclear single-quantum correlation (HSQC)-NMR techniques, reveals the chemical structural changes of pyrolysis oil during the aging process, providing insight into the mechanism of aging process.

Production of phenols and biofuels by catalytic microwave pyrolysis of lignocellulosic biomass

Catalytic microwave pyrolysis of biomass using activated carbon (AC) was investigated to determine the effects of pyrolytic conditions on the yields of phenol and phenolics. Bio-oils with high concentrations of phenol (38.9%) and phenolics (66.9%) were obtained. These levels were higher than those obtained by pyrolysis without AC addition and were closely related to the decomposition of lignin. A high concentration of esters (42.2% in the upgraded bio-oil) was obtained in the presence of Zn powder as catalyst and formic acid/ethanol as reaction medium. Most of the esters identified by GC-MS were long chain fatty acid esters. The high content of phenols and esters obtained in this study can be used as partial replacement of petroleum fuels after separation of oxygenates or as feedstock for organic syntheses in the chemical industry after purification.

The pyrolytic degradation of wood-derived lignin from pulping process

Lignin is a key component in the biomass with a complex polymeric structure of the phenyl-C(3) alkyl units. The kraft lignin from the wood pulping process is tested in TG-FTIR and Py-GC-MS. The samples are pyrolyzed in TGA coupled with FTIR from 30 to 900 degrees C at the heating rate of 20 and 40K/min. The evolution of phenolic compounds in the initial pyrolysis stage of lignin is determined by FTIR, while the second stage is mainly attributed to the production of the low molecular weight species. A bench-scale fast pyrolysis unit is employed to investigate the effect of temperature on the product yield and composition. It is found that the guaiacol-type and syringol-type compounds as the primary products of lignin pyrolysis are predominant in bio-oil, acting as the significant precursors for the formation of the derivatives such as the phenol-, cresol- and catechol-types. A series of free-radical chain-reactions, concerning the cracking of different side-chain structures and the methoxy groups on aromatic ring, are proposed to demonstrate the formation pathways for the typical compounds in bio-oil by closely relating lignin structure to the pyrolytic mechanisms. The methoxy group (-OCH(3)) is suggested to work as an important source for the formation of the small volatile species (CO, CO(2) and CH(4)) through the relevant free radical coupling reactions.

Slow pyrolysis of wood barks from Pinus brutia Ten. and product compositions

Biomass in the form of pine bark (Pinus brutia Ten.) was pyrolysed in an externally heated fixed-bed reactor. The effects of temperature and heating rate on the yields and compositions of the products were investigated. Pyrolysis runs were performed using reactor temperatures between 300 and 500 degrees C with heating rates of 7 and 40 degrees Cmin(-1). The product yields were significantly influenced by the process conditions. The bio-oil obtained at 450 degrees C, at which the liquid product yield was maximum, was analysed. It was characterized by Fourier transform infrared spectroscopy. In addition, the solid and liquid products were analysed to determine their elemental composition and calorific value. Chemical fractionation of bio-oil showed that only low quantities of hydrocarbons were present, while oxygenated and polar fractions dominated. The empirical formula of the bio-oil with heating value of 31.03 MJkg(-1) was established as CH(1.43)O(0.332)N(0.0013).

Production of monomeric phenols by thermochemical conversion of biomass: a review

Biomass is a renewable and alternative source for the production of fuels and chemicals. This paper provides a brief survey of lignin precursors as well as thermogravimetric and pyrolysis studies of lignin with special reference to the production of phenols. Thermogravimetric analysis provides information on pyrolysis kinetics while thermogravimetry in combination with mass or infrared spectrometers allowed a rapid characterization of the vapours produced by thermal treatment. Pyrolysis enabled even greater insight into the thermal behaviour of lignin. Pyrolysis of single, dimeric and trimeric model lignin compounds can determine the thermal stability of the intermediate compounds formed and the origin of the pyrolysis products. A free radical mechanism has been suggested as a major route during the early lignin degradation stages followed by a combined free radical and concerted pathway at elevated temperatures. Pyrolysis of lignin in the presence of catalysts as additives was investigated. Significant differences in terms of yields of pyrolysis products and phenolic compounds were observed. The addition of salts resulted in a high weight loss at low temperature and yielded more char than untreated wood. Some metal catalysts such as transition metals and metal oxides such as Fe2O3 and Cu exhibited a better activity in terms of selectivity for the degradation of lignin.